A low noise amplifier (LNA) is a type of electronic amplifier used in communication systems to amplify very weak signals captured by an antenna.
One of the known issues with the prior art low noise amplifiers is to ensure that the low noise amplifiers have sufficient headroom at the output to ensure that an amplified input signal is not saturated at the output. In the prior art this can be achieved by providing a bank of selectable resistors between an output node and a voltage supply. One or more resistors can be selected in order to ensure that an output signal at the output node is not saturated.